Functional and spectroscopic studies of a familial hypertrophic cardiomyopathy mutation in Motif X of cardiac myosin binding protein-C.

Authors: Brown, LJ  Singh, L  Sale, KL  Yu, B  Trent, R  Fajer, PG  Hambly, BD 
Citation: Brown LJ, etal., Eur Biophys J. 2002 Sep;31(5):400-8. Epub 2002 Jun 25.
Pubmed: (View Article at PubMed) PMID:12202917
DOI: Full-text: DOI:10.1007/s00249-002-0236-0

Familial hypertrophic cardiomyopathy is an autosomal dominant genetic disorder caused by mutations in cardiac sarcomeric proteins. One such mutation is a six amino acid duplication of residues 1248-1253 in the C-terminal immunoglobulin domain of cardiac myosin binding protein-C, referred to as Motif X. Motif X binds the myosin rod and titin. Here we investigate the structural and functional alteration in the mutant Motif X protein to understand how sarcomeric dysfunction may occur. The cDNA encoding Motif X was cloned, mutated and expressed as wild-type and mutant proteins in a bacterial expression system. Circular dichroism spectroscopy confirmed that the normal and mutant Motif X exhibited a high beta-content, as predicted for immunoglobulin domains. Thermal denaturation curves showed that Motif X unfolded with at least two structural transitions, with the first transition occurring at 63 degrees C in the wild-type but at 40 degrees C in the mutant, consistent with the mutant being structurally less stable. Sedimentation binding studies with synthetic myosin filaments revealed no significant difference in binding to myosin between the wild-type and the mutant Motif X. Molecular modeling of this duplication mutation onto an homologous IgI structure (telokin) revealed that the duplicated residues lie within the F strand of the immunoglobulin fold, on a surface of Motif X distant from residues previously implicated in myosin binding. Taken together, these data suggest that the Motif X mutation may interfere with other, as yet unidentified, functional interactions.

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CRRD ID: 1580236
Created: 2006-07-12
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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.